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<a name="gst-plugins-base-plugins-playbin3"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle"><a name="gst-plugins-base-plugins-playbin3.top_of_page"></a>playbin3</span></h2>
<p>playbin3</p>
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<td class="gallery_image" valign="top" align="right"></td>
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<div class="refsect1">
<a name="gst-plugins-base-plugins-playbin3.description"></a><h2>Description</h2>
<p>playbin3 provides a stand-alone everything-in-one abstraction for an
audio and/or video player. It differs from the previous playbin (playbin2)
by supporting publication and selection of available streams via the
<a href="/usr/share/gtk-doc/html/gstreamer-1.0/gstreamer-GstStreamCollection.html#GstStreamCollection"><span class="type">GstStreamCollection</span></a> message and <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstEvent.html#GST-EVENT-SELECT-STREAMS:CAPS"><span class="type">GST_EVENT_SELECT_STREAMS</span></a> event API.</p>
<p><span class="emphasis"><em>playbin3 is still experimental API and a technology preview.
Its behaviour and exposed API is subject to change.</em></span></p>
<p>playbin3 can handle both audio and video files and features</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>automatic file type recognition and based on that automatic
selection and usage of the right audio/video/subtitle demuxers/decoders</p></li>
<li class="listitem"><p>auxilliary files - such as external subtitles and audio tracks</p></li>
<li class="listitem"><p>visualisations for audio files</p></li>
<li class="listitem"><p>subtitle support for video files. Subtitles can be store in external
files.</p></li>
<li class="listitem"><p>stream selection between different video/audio/subtitles streams</p></li>
<li class="listitem"><p>meta info (tag) extraction</p></li>
<li class="listitem"><p>easy access to the last video sample</p></li>
<li class="listitem"><p>buffering when playing streams over a network</p></li>
<li class="listitem"><p>volume control with mute option</p></li>
</ul></div>
<div class="refsect3">
<a name="id-1.2.84.3.6"></a><h4>Usage</h4>
<p>A playbin element can be created just like any other element using
<a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElementFactory.html#gst-element-factory-make"><code class="function">gst_element_factory_make()</code></a>. The file/URI to play should be set via the <span class="type">“uri”</span>
property. This must be an absolute URI, relative file paths are not allowed.
Example URIs are file:///home/joe/movie.avi or http://www.joedoe.com/foo.ogg</p>
<p>Playbin3 is a <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstPipeline.html#GstPipeline-struct"><span class="type">GstPipeline</span></a>. It will notify the application of everything
that's happening (errors, end of stream, tags found, state changes, etc.)
by posting messages on its <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstBus.html#GstBus-struct"><span class="type">GstBus</span></a>. The application needs to watch the
bus.</p>
<p>Playback can be initiated by setting the element to PLAYING state using
<a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-set-state"><code class="function">gst_element_set_state()</code></a>. Note that the state change will take place in
the background in a separate thread, when the function returns playback
is probably not happening yet and any errors might not have occured yet.
Applications using playbin3 should ideally be written to deal with things
completely asynchroneous.</p>
<p>When playback has finished (an EOS message has been received on the bus)
or an error has occured (an ERROR message has been received on the bus) or
the user wants to play a different track, playbin3 should be set back to
READY or NULL state, then the <span class="type">“uri”</span> property should be set to the
new location and then playbin3 be set to PLAYING state again.</p>
<p>Seeking can be done using <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-seek-simple"><code class="function">gst_element_seek_simple()</code></a> or <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-seek"><code class="function">gst_element_seek()</code></a>
on the playbin3 element. Again, the seek will not be executed
instantaneously, but will be done in a background thread. When the seek
call returns the seek will most likely still be in process. An application
may wait for the seek to finish (or fail) using <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-get-state"><code class="function">gst_element_get_state()</code></a> with
-1 as the timeout, but this will block the user interface and is not
recommended at all.</p>
<p>Applications may query the current position and duration of the stream
via <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-query-position"><code class="function">gst_element_query_position()</code></a> and <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElement.html#gst-element-query-duration"><code class="function">gst_element_query_duration()</code></a> and
setting the format passed to GST_FORMAT_TIME. If the query was successful,
the duration or position will have been returned in units of nanoseconds.</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.7"></a><h4>Advanced Usage: specifying the audio and video sink</h4>
<p>By default, if no audio sink or video sink has been specified via the
<span class="type">“audio-sink”</span> or <span class="type">“video-sink”</span> property, playbin3 will use the autoaudiosink
and autovideosink elements to find the first-best available output method.
This should work in most cases, but is not always desirable. Often either
the user or application might want to specify more explicitly what to use
for audio and video output.</p>
<p>If the application wants more control over how audio or video should be
output, it may create the audio/video sink elements itself (for example
using <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstElementFactory.html#gst-element-factory-make"><code class="function">gst_element_factory_make()</code></a>) and provide them to playbin3 using the
<span class="type">“audio-sink”</span> or <span class="type">“video-sink”</span> property.</p>
<p>GNOME-based applications, for example, will usually want to create
gconfaudiosink and gconfvideosink elements and make playbin3 use those,
so that output happens to whatever the user has configured in the GNOME
Multimedia System Selector configuration dialog.</p>
<p>The sink elements do not necessarily need to be ready-made sinks. It is
possible to create container elements that look like a sink to playbin3,
but in reality contain a number of custom elements linked together. This
can be achieved by creating a <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstBin.html#GstBin-struct"><span class="type">GstBin</span></a> and putting elements in there and
linking them, and then creating a sink <a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstGhostPad.html#GstGhostPad-struct"><span class="type">GstGhostPad</span></a> for the bin and pointing
it to the sink pad of the first element within the bin. This can be used
for a number of purposes, for example to force output to a particular
format or to modify or observe the data before it is output.</p>
<p>It is also possible to 'suppress' audio and/or video output by using
'fakesink' elements (or capture it from there using the fakesink element's
"handoff" signal, which, nota bene, is fired from the streaming thread!).</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.8"></a><h4>Retrieving Tags and Other Meta Data</h4>
<p>Most of the common meta data (artist, title, etc.) can be retrieved by
watching for TAG messages on the pipeline's bus (see above).</p>
<p>Other more specific meta information like width/height/framerate of video
streams or samplerate/number of channels of audio streams can be obtained
from the negotiated caps on the sink pads of the sinks.</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.9"></a><h4>Buffering</h4>
<p>Playbin3 handles buffering automatically for the most part, but applications
need to handle parts of the buffering process as well. Whenever playbin3 is
buffering, it will post BUFFERING messages on the bus with a percentage
value that shows the progress of the buffering process. Applications need
to set playbin3 to PLAYING or PAUSED state in response to these messages.
They may also want to convey the buffering progress to the user in some
way. Here is how to extract the percentage information from the message:</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9</pre></td>
        <td class="listing_code"><pre class="programlisting"><span class="keyword">switch</span> <span class="gtkdoc opt">(</span><span class="function"><a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstMessage.html#GST-MESSAGE-TYPE:CAPS">GST_MESSAGE_TYPE</a></span> <span class="gtkdoc opt">(</span>msg<span class="gtkdoc opt">)) {</span>
  <span class="keyword">case</span> GST_MESSAGE_BUFFERING<span class="gtkdoc opt">: {</span>
    gint percent <span class="gtkdoc opt">=</span> <span class="number">0</span><span class="gtkdoc opt">;</span>
    <span class="function"><a href="/usr/share/gtk-doc/html/gstreamer-1.0/GstMessage.html#gst-message-parse-buffering">gst_message_parse_buffering</a></span> <span class="gtkdoc opt">(</span>msg<span class="gtkdoc opt">, &amp;</span>percent<span class="gtkdoc opt">);</span>
    <span class="function"><a href="/usr/share/gtk-doc/html/glib/glib-Warnings-and-Assertions.html#g-print">g_print</a></span> <span class="gtkdoc opt">(</span><span class="string">&quot;Buffering (%u percent done)&quot;</span><span class="gtkdoc opt">,</span> percent<span class="gtkdoc opt">);</span>
    <span class="keyword">break</span><span class="gtkdoc opt">;</span>
  <span class="gtkdoc opt">}</span>
  <span class="gtkdoc opt">...</span>
<span class="gtkdoc opt">}</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>Note that applications should keep/set the pipeline in the PAUSED state when
a BUFFERING message is received with a buffer percent value &lt; 100 and set
the pipeline back to PLAYING state when a BUFFERING message with a value
of 100 percent is received (if PLAYING is the desired state, that is).</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.10"></a><h4>Embedding the video window in your application</h4>
<p>By default, playbin3 (or rather the video sinks used) will create their own
window. Applications will usually want to force output to a window of their
own, however. This can be done using the <a href="../html/GstVideoOverlay.html#GstVideoOverlay-struct"><span class="type">GstVideoOverlay</span></a> interface, which most
video sinks implement. See the documentation there for more details.</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.11"></a><h4>Specifying which CD/DVD device to use</h4>
<p>The device to use for CDs/DVDs needs to be set on the source element playbin3
creates before it is opened. The most generic way of doing this is to connect
to playbin3's "source-setup" signal, which will be emitted by playbin3 when
it has created the source element for a particular URI. In the signal
callback you can check if the source element has a "device" property and set
it appropriately. In some cases the device can also be set as part of the
URI, but it depends on the elements involved if this will work or not. For
example, for DVD menu playback, the following syntax might work (if the
resindvd plugin is used): dvd://[/path/to/device]</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.12"></a><h4>Handling redirects</h4>
<p>Some elements may post 'redirect' messages on the bus to tell the
application to open another location. These are element messages containing
a structure named 'redirect' along with a 'new-location' field of string
type. The new location may be a relative or an absolute URI. Examples
for such redirects can be found in many quicktime movie trailers.</p>
</div>
<div class="refsect3">
<a name="id-1.2.84.3.13"></a><h4>Examples</h4>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1</pre></td>
        <td class="listing_code"><pre class="programlisting">gst<span class="gtkdoc opt">-</span>launch<span class="gtkdoc opt">-</span><span class="number">1.0</span> <span class="gtkdoc opt">-</span>v playbin3 uri<span class="gtkdoc opt">=</span>file<span class="gtkdoc opt">:</span><span class="gtkdoc slc">///path/to/somefile.mp4</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p>
 This will play back the given AVI video file, given that the video and
audio decoders required to decode the content are installed. Since no
special audio sink or video sink is supplied (via playbin3's audio-sink or
video-sink properties) playbin3 will try to find a suitable audio and
video sink automatically using the autoaudiosink and autovideosink elements.</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1</pre></td>
        <td class="listing_code"><pre class="programlisting">gst<span class="gtkdoc opt">-</span>launch<span class="gtkdoc opt">-</span><span class="number">1.0</span> <span class="gtkdoc opt">-</span>v playbin3 uri<span class="gtkdoc opt">=</span>cdda<span class="gtkdoc opt">:</span><span class="gtkdoc slc">//4</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p>
 This will play back track 4 on an audio CD in your disc drive (assuming
the drive is detected automatically by the plugin).</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1</pre></td>
        <td class="listing_code"><pre class="programlisting">gst<span class="gtkdoc opt">-</span>launch<span class="gtkdoc opt">-</span><span class="number">1.0</span> <span class="gtkdoc opt">-</span>v playbin3 uri<span class="gtkdoc opt">=</span>dvd<span class="gtkdoc opt">:</span><span class="gtkdoc slc">//</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p>
 This will play back the DVD in your disc drive (assuming
the drive is detected automatically by the plugin).</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="refsect2">
<a name="id-1.2.84.3.14.1"></a><h3>Element Information</h3>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">plugin</span></p></td>
<td>
            <a class="link" href="gst-plugins-base-plugins-plugin-playback.html#plugin-playback">playback</a>
          </td>
</tr>
<tr>
<td><p><span class="term">author</span></p></td>
<td>Wim Taymans &lt;wim.taymans@gmail.com&gt;</td>
</tr>
<tr>
<td><p><span class="term">class</span></p></td>
<td>Generic/Bin/Player</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="id-1.2.84.3.14.2"></a><h3>Element Pads</h3>
</div>
</div>
</div>
<div class="refsect1">
<a name="gst-plugins-base-plugins-playbin3.functions_details"></a><h2>Functions</h2>
<p></p>
</div>
<div class="refsect1">
<a name="gst-plugins-base-plugins-playbin3.other_details"></a><h2>Types and Values</h2>
</div>
</div>
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